Development of and studies on organic electronic parts using organic materials, have been conducted eagerly recently. Examples of such parts include organic electronic devices such as organic transistor, organic semiconductor laser, organic solar battery, and organic EL device. In particular, organic EL (electroluminescent) devices, promising high-quality display devices, are on the verge of commercialization. The organic EL devices, which are particularly lower in electric consumption and have various advantageous characteristics such as ultra-thin film, high-brightness light emission, and high visibility due to high self-luminescence, have been studied and developed intensively as next-generation display, planar light source, light-emitting device, and the like.
In typical configurations, the organic EL device using organic materials have a two-layer structure (single hetero structure) having an organic fluorescent material thin film (light-emitting layer) and a positive hole-transporting layer that are laminated to each other between a cathodic metal electrode and an anodic transparent electrode, a three-layer structure (double hetero structure) having an electron-transporting layer, a light-emitting layer, and a positive hole-transporting layer that are laminated to each other between a metal electrode and a transparent electrode, and the like. The positive hole-transporting layer has the functions of receiving positive holes from the anode, transporting the positive holes, and blocking electrons, while the electron-transporting layer has the functions of receiving electrons from the cathode and transporting the electrons. In addition, organic EL devices having a multilayer structure containing a positive hole-injecting layer, an electron-injecting layer or a positive hole-blocking layer, or the like additionally as needed were also developed. Each of these organic EL devices has its own unique structure functionally specialized from those of the organic EL devices having the two- or three-layer structure, for example, a structure functionally strengthened to receive positive holes or electrons or blocking leak electrons or positive holes, or allowing high brightness by more efficient recombination of electron and positive hole, improvement in durability, elongation of lifetime, or reduction in electric consumption by reduction of applied voltage.
In such light-emitting devices having organic thin films, a substrate of glass, plastic or a suitable material is placed outside the transparent electrode. Recombination of the electrons injected from a metal electrode and the positive holes injected from a transparent electrode, for example, of indium tin oxide (ITO) in the organic material thin film between the two electrodes generates excitons, which emit light in the process of emission inactivation, and the light is emitted outward via the transparent electrode and the glass substrate. Characteristically, these devices are thinner in shape and allow, for example, high-brightness light emission at a lower drive voltage, and multi-color light emission by proper choice of the light-emitting material.
In representative configuration of the organic laminated thin film light-emitting device proposed by a research group in Eastman Kodak Company, a positive hole-transporting layer of diamine compound, light-emitting and also electron-transporting layers of tris(8-quinolinolato)aluminum complex, and a cathode of Mg:Ag (alloy) are formed in that order on an ITO glass substrate.
For producing for full-color displays, devices having blue, green, and red light-emitting devices coated on a substrate separately are now studied. Among the light-emitting devices, the green light-emitting material, which is formed by vapor deposition of a low-molecular weight compound, is higher in maturity and closer to commercialization, at a level superior in practicality such as brightness and durability. However, the red and blue light-emitting materials are left delayed in development, and in particular in red light-emitting materials, there is a problem that there are no such light-emitting materials that are superior in durability and show sufficient brightness and color purity. An orange device relatively higher in efficiency was prepared for production of a multi-colored display, but currently, the efficiency is still insufficient and the material expensive. Because of the problem of device deterioration, devices emitting white light have also been studied intensively. Even with these white light-emitting materials, there is also the problem that there are no materials that are superior in durability and show sufficient brightness and sufficient color purity.
Examples of the red light-emitting materials include perylenes such as bis(diisopropylphenyl)perylene, porphyrins, europium complexes, julolidine-substituted styryl compounds (e.g., Japanese Patent Application Laid-Open (JP-A) No. 2001-43974), and the like. The emission color (emission wavelength) is adjusted to a desired color used by doping method, i.e., by adding a trace amount of red fluorescence compound into the host material as a dopant. Examples of the host materials include metal complexes of quinolinol derivatives such as tris(8-quinolinolato)aluminum complex, bis(10-benzoquinolinolato)beryllium complexes, diarylbutadiene derivatives, stilbene derivatives, benzoxazole derivatives, benzothiazole derivatives, perynone derivatives, and the like. Examples of the dopants include red fluorescence compounds such as 4-(dicyanomethylene)-2-methyl-6-(p-dimethylaminostyryl)-4H-pyran (DCM), metalphthalocyanine compounds (MgPc, AlPcCl, etc.), squarylium compounds, coumarin compounds (see e.g., JP-A No. 10-060427), violanthrone compounds, nailered, 5-cyanopyrromethene-BF4 complexes (see e.g., JP-A No. 11-176572); and red emission light is obtained by doping the host material with the compound.
However, among those light-emitting materials (host and dopant materials) commonly used in the art, there are many light-emitting materials that have inferior luminous efficiency prohibiting high brightness, have poor color purity and a pale orange emission light only even when doped, or have low durability and a shortened lifetime of the device; thus, there exists a serious problem that there is no material satisfying the requirements in color purity and brightness at the same time. In addition, the orange light-emitting devices are still unsatisfactory in efficiency. Further, there is currently no white device for use as backlight or others that are higher in brightness and in luminous efficiency, longer in lifetime, and favorable in color purity.
In such a light-emitting device, a transparent electrode formed on a glass or polymer substrate is generally used as an anode; and a positive hole-injecting layer, a positive hole-transporting layer, and others are normally formed thereon. These transparent electrodes for example of ITO generally have a work function significantly different from that of the positive hole-transporting layer, and are different in energy level from the positive hole-transporting layer and adhesion between the ITO layer and the positive hole-transporting layer is poorer, which occasionally lead to crystallization of the positive hole-transporting layer and decrease in efficiency due to higher applied voltage, consequently causing instability during operation. Although a method of forming the transparent electrode, for example, of ITO lastly, similarly to the top emission structure, was studied recently, there was still the problem of similar deterioration in efficiency.
Examples of the materials for the positive hole-injecting layer include the phthalocyanine derivatives described in JP-A Nos. 57-51781, 63-295695and 8-199161; the low-molecular weight compounds such as thiophene derivatives (see JP-A No. 5-94877), aromatic amine derivatives (see JP-A No. 8-269445), hydrazone derivatives (see JP-A No. 4-320483); and polymers such as polythiophene, polyaniline, polythienylene vinylene, and polyphenylene vinylene (see JP-A No. 4-145192); and the like.
However, there are still problems at long-term operational stability, lifetime, luminescence brightness, luminous efficiency, and others. To overcome these problems, it is quite important to develop an inexpensive material having sufficiently high optical and mechanical properties that is favorable in coating properties and suitable for mass production. In particular, devices containing a phthalocyanine derivative as a positive hole-injecting material have been widely used because they are relatively better, but the injection efficiency is still unsatisfactory and the luminous efficiency of the devices remains to be improved. In addition, the phthalocyanine derivative, which is used as a blue pigment, often caused the problem that absorbing a red emission light, changed the emission color and decreased the luminous efficiency. Use of other low-molecular weight positive hole-injecting materials also often carried the problem that the devices are inferior in stability and heat resistance because of their low glass transition and melting points, while use of polymer positive hole-injecting materials often carried the problem that it was difficult to form a uniform film by wet casting and the lifetime of the device was shorter. Phosphorescence devices particularly superior in internal quantum efficiency are attracting attentions recently, and for improvement of the efficiency thereof, it is necessary to develop a stable material for positive hole-injecting layers.
The condensed polycyclic compounds described in the invention (see e.g., E. Clar, W. Kelly, D. G. Stewart, J. W. Wright, J. Chem. Soc., (1956), 2652; Tokita, Arai, Ohoka, Nishi, Nippon Kagakukaishi JP, 1989, (5), 876; J. Photopolym. Sci. Technol., 11, 41 (1998); Tokita, Arai, Toya, Nishi, Nippon Kagakukaishi JP, 1988, (5), 814; Tokita, Suga, Toya, Nishi, Nippon Kagakukaishi JP, 1988, (1), 97; Mol. Cryst. Liq. Cryst., 1994, Vol. 246, 119; R. Schmidt, W. Drews, H.-D. Brauer, Journal of Photochemistry, 18 (1982), 365; Daisuke Goma, Masao Ken, Sumio Tokita, Journal of Photopolymer Science and Technology, 14, 2(2001), 239] have been studied in detail as a photochromic material that changes its color by irradiation of a particular light or by application of heat, but there is almost no report on application thereof to organic electronic parts, and the kinds of the derivatives investigated are limited; and thus, there exist an urgent need for a new material.
In addition, for production of a compound having the basic skeleton represented by Formula (1) or (2) described below by conducting ring closure of a compound having the basic skeleton represented by Formula (8) or (9) described below, a method of melting and ring-closing a compound in anhydrous aluminum chloride and sodium chloride (for example, E. Clar, W. Kelly, D. G. Stewart, J. W. Wright, J. Chem. Soc., (1956), 2652); a method of melting and ring-closing a compound in anhydrous aluminum chloride, sodium chloride, and hydroquinone (e.g., JP-A No. 6-56777 and Tokita, Arai, Toya, Nishi, Nippon Kagakukaishi JP, 1988, (5), 814; R. Schmidt, W. Drews, H.-D. Brauer Journal of Photochemistry, 18 (1982), 365; and Daisuke Goma, Masao Ken, Sumio Tokita journal of Photopolymer Science and Technology, 14, 2(2001), 239), and other have been reported. However, all of these methods were not proper as a commercial method, as the ring closure reactions are inferior in workability because they are carried out in the absence of solvent and the methods give chloride salts of Formula (1) or (2) as byproducts.